Infrared scanning system for material testing

ABSTRACT

Herein described is an infra-red scanning system which includes a rotating scanning block. Reflecting mirrors are disposed about the vertical perphery of the block and are adapted to rotate therewith. A motor including a cam and follower causes the scanning block to continuously nod during the scanning thereof. A workpiece may then be disposed in the path of the scanner and thermal radiations therefrom are reflected to an infra-red detector. A folding mirror system is disposed between the detector and the workpiece and is used to focus the thermal energy to the detector. To decrease the obscurations within the field of view an aperture is placed in the center of the folding mirror and the detector is placed behind the aperture in the folding mirror in alignment with the primary mirror. The thermal energy is then focused from the reflective scanner through the hole in the folding mirror to the detector.

[ 1March 13, 1973 Apple INFRARED SCANNING SYSTEM FOR MATERIAL TESTING[75] Inventor: Wayne Richard Apple, Boulder,

[73] Assignee: Automation Industries, Inc., Los

Angeles, Calif.

[22] Filed: Feb. 3, 1971 [21] Appl. No.: 112,119

[52] US. Cl ..250/83.3 H [51.] Int. Cl.I ..G01j l/04 [58] Field ofSearch ..250/83.3 H, 83.3 HP

[56] References Cited UNITED STATES PATENTS 3,118,062 1/1964 llgenfritzet a1 ..250/83.3 H 3,209,149 9/1965 Tucker 250/833 H X 3,219,822 11/1965Kutzscher et al.. ..250/83.3 H 3,283,148 11/1966 Schwarz et al.........250/83.3 HP X 3,287,559 11/1966 Barnes.... .....250/83'.3 HP X3,597,617 8/1971 Passaro ..250/83.3 HP

Primary ExaminerArchie R. Borchelt Attorney-Dan R. Sadler [57] ABSTRACTHerein described is an infra-red scanning system which includes arotating scanning block. Reflecting mirrors are disposed about thevertical perphery of the block and are adapted to rotate therewith. Amotor including a cam and follower causes the scanning block tocontinuously nod during the scanning thereof. A workpiece may then bedisposed in the path of the scanner and thermal radiations therefrom arereflected to an infra-red detector. A folding mirror system is disposedbetween the detector and the workpiece and is used to focus the thermalenergy to the detector. To decrease the obscurations within the field ofview an aperture is placed in the center of the folding mirror and thedetector is placed behind the aperture in the folding mirror inalignment with the primary mirror. The thermal energy is then focusedfrom the reflective scanner through the hole in the folding mirror tothe detector.

4 Claims, 8 Drawing Figures PATENTEB 31913 3.720.832

SHEET 10F 4 Fig. l Fig. 2.

PRIOR ART PRIOR ART lOO From Detector l2 Vertical Sweep Genera lor 5Horizontal Sweep Generator Wayne R. Apple lNVENTOR.

ATTORNEY PATENTEDHARI 3|975 3 7 0, 32

SHEET 2 [IF 4 Dotcctor ,/I2

Amplifier Horizontol' Swap Gene rotor Wayne R. Apple,

INVENTOR.

@fhiik ATTORNEY.

PATENTEUHAMIBH 3, 0, 32

SHEET 3 OF 4.

Wayne R. Apple,

INVENTOR.

AT TOR N EY.

INFRARED SCANNING SYSTEM FOR MATERIAL TESTING BACKGROUND This inventionrelates to scanning systems and more particularly to a novel andimproved scanning system useful, for example, in the scanning of aworkpiece which emits infrared radiations. The system further relates toa novel and improved optic system disposed within the field of view ofthe detector and the workpiece. Further, this invention relates to anoptical scanning system which includes a multi-sided mirror adapted torotate and scan the workpiece and includes means for causing therotating scanner to nod during the revolution thereof.

In the prior art several types of nondestructive test systems areavailable which are capable of inspecting some form of energy into orthrough the workpiece and observe the manner in which the workpiece andthe energy interreact. Of all the forms of energy which have beenemployed for this purpose, ultrasonic, magnetic, eddy current, X-ray,etc., are most suitable for commercial purposes.

In recent years numerous attempts have been made to develop acommercially satisfactory nondestructive tester employing infra-red andother thermal energies. It is known that thermal conductivity of aworkpiece is a function of the type of material. However, the thermalconductivity of the workpiece is also greatly affected by variations ofsuch factors as porosity, voids, inclusions, grain structure, etc. Sincethermal conductivity controls the flow of heat, if there are localvariations in any of these characteristics, there will be correspondinglocal variations in the manner in which temperature in the workpiecevaries. As a result, the temperatures of the incremental areas of thesurface of the workpiece will vary at different rates as the temperatureof the workpiece changes. It is thus possible to,

determine the various characteristics of a workpiece and particularlythe presence of internal defects, i.e., a void and inclusion, avariation in the thickness, etc., by observing the surface temperatureof the workpiece.

Another type of use of infra-red scanning apparatus is to test anddiagnose the human body for variations therein. It is known that thehuman body emits thermal energy in its own mode. By scanning thetemperature gradients of the human body, a diagnostic aid is availablewhenever diseases or injury produces variations in the skin temperature.This type of scanning can provide early diagnosis and study of varioustypes of tumors, malignancy of bone and soft tissues inflammatoryprocesses within the human body and the like.

Further, it is possible to use, an infra-red scanning system to providethermal images, especially of a human body which emits the abovementioned thermal energy. Thus, by appropriate scanning methods, thermalfacsimiles are provided to show a reproduction of the body which isscanned. The infra-red detector responds to the infra-red radiationnaturally emitted by these objects.

In operation an optical system scans the field of view of a highlysensitive infra-red detector across the target. The collected radiationis converted into proportional electrical signals. These signals canthen be amplified, processed and displayed on a cathode ray tube, forexample, in the form ofa thermal image or on a facsimile recorder. Fromthis display target temperature can be determined if the emissivity ofthe target is known.

These thermal images show the temperature distribution over the surfaceof the target in shades whereby warmer areas are light and coolerregions are darker or the other way around depending upon the desiredrecording image. Such a visual display provides investigators withinformation concerning the nature of the target and inferences as to thesubsurface conditions. This information is often unobtainable by otherprior art devices. The thermal images may then be photographed toproduce thermograms, that is, permanent records of the targets heatdistribution. In some cases the images may be recorded directly upon athermogram. Since such infra-red measurements require no physicalcontact with the target, observations can be made without disturbing thetargets natural environment in any way.

SUMMARY Briefly described, the present invention includes, in theembodiment shown, an infra-red scanning system which includes a rotatingmirror. The described embodiment illustrates a four-sided block havingmirrored surfaces about the vertical sides thereof. It should beunderstood that any number of sides are possible and still remain withinthe spirit and scope of the present invention. For example, three sidedor six sided mirrors. The rotating mirror is slewed as it riotates tocomplete a raster scan of a workpiece. The workpiece may be of the typewhich emits thermal radiations in its own mode and exhibits a differencein the radiation emitted therefrom as a function of the structure andsubstructures of the workpiece. For example, the workpiece being scannedmay be a sheet of preheated metal or a human body.

Reflections from the rotating mirror which are indications of thetemperature of the workpiece are then presented to a folding mirror andback to a primary spherical mirror. This latter mirror focuses thereflective beam back through an aperture in the folding mirror where itis detected by an infra-red detector. With the detector positionedbehind the folding mirror and in the path of the focused energy from theprimary mirror, a reduced obscuration in the field of view is therebyprovided. This allows the folding mirror to be disposed exactly in frontof the primary mirror and thereby reduce the overall size of the opticsof the system with this reduced obscuration.

There are presently a number of patents in the prior art which teach theconcept of thermal infra-red detecting systems. For example, US. Pat.Nos. 3,483,721; 3,451,254; 3,434,332; 3,433,052; 3,427,861, 3,401,551;3,504,524; and 3,462,602 all of which are incorporated herein byreference. All of these patents are assigned of record to AutomationIndustries, Inc., the assignee of the present invention.

DRAWINGS These and other features and advantages will become moreapparent to those skilled in the art when taken into consideration withthe following detailed description where like reference numeralsindicate like and corresponding parts throughout the several views andwherein:

FIGS. 1 and 2 illustrate prior art optic systems which are now in useshowing the optic system ofinfra-red detectors and scanners;

FIG. 3 is a schematic drawing illustrating one embodiment of the opticsystem used in accordance with the present invention;

FIG. 4 is a schematic drawing illustrating the positions of variouscomponents in accordance with the present invention;

FIG. 5 is a side view illustrating the scanning system in accordancewith the present invention;

FIG. 6 is a view of the scanning system taken of FIG. 5 with the mirrorremoved for ease in viewing the scan structure;

FIG. 7 is a schematic block diagram illustrating electronic systems usedwith the infra-red scanning device in accordance with one embodiment ofthe present invention; and

FIG. 8 is a semi-schematic and partial perspective view of anotherembodiment of a readout means in accordance with the principles of thisinvention.

DESCRIPTION Turning now to a more detailed description of this inventionand particularly in relation to prior art optic systems, reference isnow made to FIG. ll whereby a target position 10 is illustrated asemitting thermal energy to be detector by a detector 12. The target 10may be a workpiece which emits thermal energy, for example, a piece ofhot rolling stock from a steel mill. On the other hand, it may be ahuman body which naturally emits thermal energy in its own mode.

In order to focus the received thermal energy from the target 10 to thedetector 12, certain focusing and folding mirrors are used. For example,a primary or focusing mirror 14 is positioned within the field of viewof the target 10. Mirror 14 is generally concave in shape and focusesthe thermal energy to a single focal point. A folding mirror 16 isprovided to reflect the thermal energy towards the detector 12 in orderto place the detector 12 outside of the optics field of view and thusreduce obscuration. It can be noted that a certain area of obscuration(area 20) is caused by the mirror 16 between the target 10 and thefocusing mirror I4. Thus all of the target energy is not directlydetected by the detector 12.

FIG. 2 illustrates yet another prior art method of folding the focusedreturn infra-red images to the detector 12 but in this embodiment it canstill be seen that a sufficient area 20 obstructs the infra-red energyradiated towards the detector 12. In this embodiment the folding mirror16 is placed directly between the primary focusing mirror 14 and thetarget 10 whereby the folded and reflected infra-red energy is focusedthrough a hole 22 within the primary focusing mirror I4. Still, through,a large obstruction area 20 is within the radiated infra-red energyfield.

With reference now to FIG. 3 there is shown a folding mirror system inaccordance with one aspect of this invention. By this embodiment thefolding mirror 16 is directly in the path of the radiated beam of theimage produced by the target 10. The folding mirror 16 then reflects theradiant thermal energy towards the primary collecting and focusingmirror 14. The mirror 14 is generally spherical in shape and focuses thethermal energy back through an aperture 24 in the folding mirror I6 todetect the energy received from the target 10 and focused thereto. Itcan be noted by this latter improved method that the area of obstruction(area 20) is reduced to a minimal and in face no larger in area than thesize of the aperture 24 in the folding mirror 16.

FIG. 4 illustrates a scanning system using the principles of the opticsystem set forth in FIG. 3. In this embodiment a four-sided member 26 isused which extends on a vertical axis 28 and has four verticalreflective surfaces thereon. To accomplish the four-sided structure acube shaped block is used with the reflective surfaces being mirrors.The member 26 is positioned within the line of sight of the foldingmirror 16 and directs the energy from the target 10 towards the foldingmirror 16 whereby it is reflected onto the focusing mirror I4 and backthrough the aperture 24 to the detector I2.

Means are included to rotate the member 26 as shown on the vertical axis28 so that a scan is made across the target 20 as illustrated by thescan paths 30. Because the member 26 is rotating in a single direction,the scan in this particularly embodiment, as shown in FIG. 4, alwaysgoes in a single direction across the workpiece l0 and in thisembodiment as shown going from left to right thereon. In order to scanthe workpiece ]10 from the top to its bottom, means are included to slewthe rotating mirror 26 on a slew axis 32.

Referring now to FIGS. 5 and 6, there is shown a practical embodiment ofthe present invention to provide for the rotating of the member 26 onthe axis 28 and the slewing of the member 26 on the axis 32. Theapparatus comprising the shown and described embodiment is positioned ona base plate or frame 38. A vertical extending angle plate 40 isattached to frame 38 in a suitable manner. The vertical extending angleplate 40 has an opening 34 near the top end 35 thereof to receive ashaft 46. The shaft 46 is fixedly mounted to a frame 48 and is rotatablymounted to angle plate 40 through suitable bearing 49. Connection ofshaft 46 through opening 34 of angle plate 40 and to frame 48 can beaccomplished in any suitable manner. A motor 50 is mounted to a frame 38by suitable screws 52. A pulley 54 is coupled to shaft 56 of motor 50. Ashaft 58 extends through plate 40 and suitable bearings 60. A pulley 62is coupled to one end of shaft 58 and is con nected to pulley 54 with adrive belt 64.

A frame 48 which is substantially C-shaped is provided and includes topand bottom extending arms 68 and 78. A vertical extending plate 72extends between the top plate 68 and bottom plate and is screwed thereonby the suitable screws 74.

A plate 78 extends outwardly from the top plate 68 of frame 48. A motor80 is mounted on extension plate 78 and is connected to the shaft 28 ofrotating mirror 26 by suitable gears 82 and 83 to impart rotationthereto.

An eccentric cam 84 is connected to shaft 58 which is positioned on theside opposite pulley 62. The C- shaped frame 48 has a cutout portion 86so that cam 84 can rotate without obstruction therefrom. The cutout 86of the C-shaped frame 48 has a protrusion which forms a cam follower 88thereon. As the cam 84 rotates, it rides on follower 88 causing theframe 48 to tilt and thereby tilt mirror 26 causing it to scan theworkpiece 10. When the follower 88 reaches the cutout 89 in cam 84, theframe 48 drops back to its original start position assisted by thespring 90 connected between plate 78 and the bottom of plate 40.

The output of detector 12 is an electrical signal which is directlyproportional to the amount of thermal energy impinging thereon. Thissignal is applied through an amplifier 100, as shown in FIG. 7, to thegrid 102, of a cathode ray tube 104. A vertical sweep generator 106 anda horizontal sweep generator 108 are coupled directly to the verticaldeflection plates 110 of cathode ray tube 104 and horizontal deflectionplates 112 of cathode ray tube 104, respectively. Vertical sweepgenerator 106 is triggered by a pulse vertical scan with relation to theexact slew position of the slew motor 48. Thus each tilt position of therotating mirror is applied in the form of electrical pulse to theterminal 114 whereby it indexes the sweep vertical generator 106 is asuitable manner.

Likewise the scan position of the rotating mirror as dictated by themotor 80 is applied as an electrical pulse to the terminal 116 andapplied to the horizontal sweep generator 108 which causes the sweepsignal to sweep across the face of the cathode ray tube 104. Thus thesignal from the detector 22 after being amplified and processed isdisplayed on the cathode ray tube 104 as an intensity modulated rasterand a thermal image of its target, i.e., the object being scanned.

FIG. 8 illustrates a further embodiment of a readout/record system ofthis invention which is a fast scan single line which records onadvancing recording paper. A CRT 120 is included which has the gridthereof connected through a suitable amplifier 122 from a detector 12. Ahorizontal sweep generator 124 is connected to the horizontal deflectionelectrodes in CRT 120. The horizontal sweep is matched with the rotatingmotions of the mirror 26. A suitable recording paper 128 is advanced infront of the CRT 120 and is developed in response to the electron beamthereon. The recording paper is in synchronism with the scan of theworkpiece 10. As the mirror 26 is scanned from top to bottom on theworkpiece 10, the recording paper moves past the CRT at the same rate.The CRT 120 is modulated with the output of detector 12, therebyrecording the thermal image on the paper 128.

These signals received from the position of the detector and triggerposition of the scans from each of the positions of the rotating mirrorand the position of the slew motor can also be applied directly into athermal facsimile machine which can show thermal facsimiles of thedevice actually being scanned, whereas the darker portions and lighterportions of the thermal image will be dependent upon the intensity ofthe infrared radiation received by the detector 12.

Thus having shown but one preferred embodiment of this invention, whatis claimed is:

1. In combination:

a base including a vertically extending member;

a first horizontal shaft rotatably coupled through the extending memberof said base;

a frame coupled to said first shaft, said frame being spaced from saidbase and pivotally movable about said first shaft in respect to saidbase, said frame having a cam follower thereon;

a multi-sided mirror rotatably mounted to said frame about a verticalaxis a second shaft rotatably coupled through said extending member ofsaid base, said second shaft being parallel to said first shaft; and

an eccentric cam coupled to said second shaft and positioned to engagethe cam follower on said frame, whereby rotation of said second shaftimparts tilting movement to said mirror in respect to said base.

2. In the combination as defined in claim 1 wherein said frame beingsubstantially C-shaped having a top member, a bottom member and avertical member coupled between said top and bottom member, said firstshaft being secured to said vertical member, said vertical memberincluding a cutout portion, said eccentric cam being located within saidcutout portion, said cam follower located within said cutout portion andin continuous engagement with said cam.

3. The combination of claim 2 including:

a biasing means connected between said base and said frame, said biasingmeans exerting a continuous bias upon said frame tending to maintainsaid follower in contact with said cam.

4. The combination as defined in claim 3 wherein:

said biasing means comprises a spring.

1. In combination: a base including a vertically extending member; afirst horizontal shaft rotatably coupled through the extending member ofsaid base; a frame coupled to said first shaft, said frame being spacedfrom said base and pivotally movable about said first shaft in respectto said base, said frame having a cam follower thereon; a multi-sidedmirror rotatably mounted to said frame about a vertical axis; a secondshaft rotatably coupled through said extending member of said base, saidsecond shaft being parallel to said first shaft; and an eccentric camcoupled to said second shaft and positioned to engage the cam followeron said frame, whereby rotation of said second shaft imparts tiltingmovement to said mirror in respect to said base.
 1. In combination: abase including a vertically extending member; a first horizontal shaftrotatably coupled through the extending member of said base; a framecoupled to said first shaft, said frame being spaced from said base andpivotally movable about said first shaft in respect to said base, saidframe having a cam follower thereon; a multi-sided mirror rotatablymounted to said frame about a vertical axis; a second shaft rotatablycoupled through said extending member of said base, said second shaftbeing parallel to said first shaft; and an eccentric cam coupled to saidsecond shaft and positioned to engage the cam follower on said frame,whereby rotation of said second shaft imparts tilting movement to saidmirror in respect to said base.
 2. In the combination as defined inclaim 1 wherein said frame being substantially C-shaped having a topmember, a bottom member and a vertical member coupled between said topand bottom member, said first shaft being secured to said verticalmember, said vertical member including a cutout portion, said eccentriccam being located within said cutout portion, said cam follower locatedwithin said cutout portion and in continuous engagement with said cam.3. The combination of claim 2 including: a biasing means connectedbetween said base and said frame, said biasing means exerting acontinuous bias upon said frame tending to maintain said follower incontact with said cam.